The overall goal of this project is to discover the mechanism and control of the secretion and resorption of molting fluid in insects. The study will be conducted on the larval-pupal transformation in Saturniid and Sphyngid insects, where it can be studied by rigorous biophysical techniques, such as short-circuiting, unidirectional flux determinations and flux ratio analysis, and competition by other monovalent or divalent cations. Properties of potassium transport during secretion and bicarbonate transport during resorption of molting fluid across the pharate pupal integument (PPI) will be studied, as will the effects of divalent metal cations on this transport. The nature of insect potassium specific ionophores and ionophoroproteins will be investigated and their patterns of change correlated with the capacity of the PPI to actively transport potassium and bicarbonate. This system will be used as a model for molting events in vector insects and pests, where it has medical and environmental value.